1. Field of the Invention
The present invention generally relates to a method and an apparatus for liquid phase deposition, and more particularly, to a method and an apparatus essential for forming a metal/non-metal thin film on a semiconductor substrate via chemical deposition.
2. Description of the Prior Art
In recent years, the fabrication techniques for both ultra large scale integrated circuits (ULSI) and liquid crystal displays (LCDs) tend towards lower temperatures in order to avoid degradation of the device characteristics due to the thermal stress on the thin films. Owing to novel low-temperature related techniques, various low melting-point substrates such as glass substrates and plastic substrates are suitable for use in growth of high-quality thin films with low thermal stress at low temperatures. Therefore, development in low-temperature related techniques has attracted tremendous attention in the industry.
It is well known that silicon oxide is a very important material in the field of semiconductor. Silicon oxide has different applications according to its growing conditions. In early days, silicon oxide was grown in the furnace in the temperature range from 700 to 1000xc2x0 C. With the improvement in fabrication techniques, a novel silicon oxide growing method known as plasma-enhanced chemical vapor phase deposition (PECVD) has been developed and successfully demonstrated in the temperature range from 300 to 400xc2x0 C. However, it is notable that such a temperature range for silicon oxide growth by using plasma is still too high for deep sub-micron fabrication process, which may lead to device damage during PECVD operation. Later, high-vacuum sputtering was proposed but limited by its low throughput and possible ion leakage. Accordingly, the fabrication techniques of the new generation for both ultra large scale integrated circuits (ULSI) and liquid crystal displays (LCDs) tend towards lower temperatures. It is beneficial to develop a low-temperature technique for silicon oxide growth without using plasma.
Generally, only low-temperature liquid phase deposition stations are provided with a wet trough. However, the contaminative particles generated in the wet trough make the control difficult for temperature, on-line monitoring system, solution supply, and cleaning, which may cause trouble in on-line mass production techniques. Especially, in the 0.18 xe2x96xa1m fabrication process, there is danger in that the chemical vapor in the wet trough may produce contaminants.
Therefore, the present invention provides a method and an apparatus for liquid phase deposition, which employs a closed-loop filter system in order to eliminate contaminative particles during low-temperature liquid phase deposition operation on the substrate. It is advantageous for its easy control and specially designed closed-loop dual-trough system with a steady flow, so as to overcome the problems in the prior art, improve the uniformity of thin film deposition, and achieve the objects of high throughput, high fabrication yield, and low fabrication cost.
It is the primary object of the present invention to provide an apparatus for liquid phase deposition, and more particularly, an apparatus essential for forming a metal/non-metal thin film on a semiconductor substrate via chemical deposition with high reliability.
It is another object of the present invention to provide a method for liquid phase deposition on a semiconductor substrate, so as to provide high fabrication yield, and eliminate contaminative particles, especially in the 0.18 xe2x96xa1m fabrication process.
It is still another object of the present invention to provide a method and an apparatus, employing a specially designed closed-loop filter system in order to fabricate high quality thin films with low thermal stress by performing low-temperature liquid phase deposition operation on a substrate.
In order to achieve the foregoing objects, present invention provides an apparatus for liquid phase deposition, comprising:
a saturation reaction system, including a mixture trough, at least two supply devices for raw materials, a stirrer device, a filter device, and valve control devices;
a steady-flow over-saturation loop reaction system, including an over-saturation reaction trough, at least one liquid level control trough, at least two supply devices for raw materials, a stirrer device, a filter device, and valve control devices;
an automatic solution concentration monitoring system, for controlling the reactant concentrations; and
a waste liquid recycling system, comprising at least two storage troughs, a recycled waste liquid level sensor, a recycled waste liquid sensor, and valve control devices.
The present invention also provides a method for liquid phase deposition, comprising the steps of:
providing at least two raw materials from said at least two supply devices of said saturation reaction system into said mixture trough; after stirring by said stirrer device until saturation, filtering out unnecessary solid-state particles by using said filter device; providing saturated and filtered liquid by using said pumps through said valve control devices into said over-saturation reaction trough of said steady-flow over-saturation loop reaction system; stopping providing said saturated and filtered liquid when said over-saturation reaction trough is filled up with said saturated and filtered liquid and said saturated and filtered liquid over-flows into said at least one liquid level control trough to a pre-determined level; switching said valve control devices into a state in which said steady-flow over-saturation loop reaction system runs independently; providing a substrate into said over-saturation reaction trough; providing reactants from said at least two supply devices into said over-saturation reaction trough; and depositing a thin film onto said substrate when said saturated liquid becomes over-saturated.
During the reaction, the generated particles can be filtered out by said filter device, and the reaction conditions can be controlled by said recycled waste liquid level sensor and said heater so as to obtain high-quality thin films.